The present invention relates to structural beams used as bumper reinforcement beams in vehicle bumper systems, although the present innovation is not limited to only vehicle bumper systems.
Many reinforcement beams in vehicle bumper systems are roll formed, due to the advantages in high volume of dimensional consistency and low cost. In roll forming processes, a sheet is typically rolled into a constant cross section (e.g. tubular or open channel) and then cut to length. Sometimes the beam is longitudinally curved (called “sweeping”) as part of the roll forming process or as a secondary operation after the roll forming process. For example, see Sturrus U.S. Pat. Nos. 5,454,504, and 5,104,026 and 6,240,820. Low weight and high strength-to-weight ratio are important properties in bumper reinforcement beams since heavier vehicles get lower gas mileage and tend to emit greater amounts of pollution. Further, lower weight can mean less material and lower part costs. However, an improvement is desired that maintains functional requirements of a particular bumper reinforcement beam, but that reduces weight and provides optimized strength-to-weight ratio. Also, an improvement is desired that optimizes torsional and bending strength in longitudinal areas along a length of the beam while minimizing weight.